The prior art contains several references to the use of attapulgite or palygorskite clays to stabilize suspensions. U.S. Pat. No. 4,069,034, issued to Hoover on Jan. 17, 1978, indicates that attapulgite clays or bentonite clays can be used as suspending aids in suspension fertilizers. (Suspension fertilizers are aqueous slurries of a crystalline fertilizer component in a saturated aqueous solution of the component; they are made by partially recrystallizing the crystalline component from a supersaturated aqueous solution.) Hoover is distinguishable from the present invention not only because Hoover requires an aqueous solution, but also because it suggests that the solutions are not completely stable unless another ingredient, humic acid, is added to the composition.
Two of the prior art references relate to the use of several clays, including attapulgite and palygorskite clays, as suspension aids for liquid scouring cleansers. These patents are U.S. Pat. No. 4,051,055, issued to Trinh et al. on Sept. 27, 1977; and U.S. Pat. No. 4,005,027, issed to Hartman on Jan. 25, 1977. Again, however, the latter two references describe only aqueous suspensions, rather than nonaqueous or only slightly aqueous suspensions.
U.S. Pat. No. 4,166,039, issued to Wise on August 28, 1979, teaches that certain clays may be used to improve the homogeneity of crutcher mixes, but teaches that attapulgite clays are not useful for this purpose if the crutcher mixes contain a high proportion of a nonionic surfactant.
Several of the prior art references discuss ways in which to produce physically stable compositions which contain no water. U.S. Pat. No. 4,018,720, issued to Lengyel et al. on April 19, 1977, and U.S. Pat. No. 2,864,770, issued to McCune on Dec. 16, 1958, each contemplate the use of a nonionic surfactant as the vehicle in a detergent mull, but require at least some of the suspended builders to be in the form of very small particles in order to produce a stable composition. U.S. Pat. No. 3,630,929, issued to van Dijk on Dec. 28, 1971, teaches the use of highly voluminous inorganic carrier materials such as silica, alumina, magnesia, ferric oxide, titanium oxide, and the like as suspending agents for a very high proportion of an insoluble builder material in a paste consisting largely of a liquid detergent surfactant. No clays are disclosed in van Dijk as carrier materials. Also, the van Dijk reference states that the particle size of the suspended particles must be less than about 300 microns, preferably less than about 200 microns, in order for the suspension to be stable. United Kingdom patent application No. 2,017,072, filed by NL Industries, Inc., published Sept. 28, 1979, teaches the use of certain quaternary ammonium clays as suspending agents in nonaqueous systems.
Three references teach the use of unrelated clays as suspending agents. They are U.S. Pat. No. 3,259,574, issued to Morrison et al. on July 5, 1966; U.S. Pat. No. 3,557,037, issued to Collins et al. on Jan. 19, 1971; and U.S. Pat. No. 3,549,542 issued to Holderby on Dec. 22, 1970. Finally, the following references show the use of clays in unrelated contexts, particularly in fabric softening: U.S. Pat. No. 3,954,632, issued to Gloss on May 4, 1976; U.S. Pat. No. 3,948,790, issued to Speakman on Apr. 6, 1976; and British Pat. No. 1,519,605, issued to Perruchot on Aug. 2, 1978.